1. Field of the Invention
The present invention relates to a ferroelectric recording medium that permits the recording of information by reversing the polarization of a ferroelectric material, and to a method of manufacturing the same.
The present invention further relates to an information processing device comprising the above ferroelectric recording medium, and to a method of processing information employing the above ferroelectric recording medium.
2. Discussion of the Background
Means of rapidly transmitting terabyte levels of information have developed to a marked degree in recent years, permitting the transmission of images and data comprised of vast quantities of information. As data transmission techniques have improved, the achievement of higher recording capacity has become necessary in recording and reproducing devices and recording media for recording, reproducing, and storing information. However, the recording density in magnetic recording, typified by hard disc drives (HDDs), is limited by thermal fluctuation to about 100 Gbit/inch in longitudinal recording, and to about 1 Tbit/inch2 even in perpendicular recording. Thermal recording media are known. However, due to the intervention of thermal conduction, these media are capable of achieving recording densities of about 500 Gbit/inch2 to 1 Tbit/inch2.
A recording method utilizing the spontaneous polarization of ferroelectric materials (ferroelectric recording) has been attracting attention among high-capacity recording media in recent years. In ferroelectric recording, utilization of the spontaneous polarization of a ferroelectric material with the application of an external electric field presents the possibility of achieving high capacities greatly exceeding those achieved by conventional recording methods.
When recording information on a ferroelectric recording medium, by scanning an electrically conductive probe of a scanning tunneling microscope (STM), an atomic force microscope (AFM), or the like over a ferroelectric recording layer formed on an electrode layer, an electric field is applied between the probe and the electrode layer. The electric field reverses the polarization in the ferroelectric recording layer to cause minute domains (polarization regions) to form. The information thus recorded can also be read by scanning an electrically conductive probe over the ferroelectric recording layer. In such a recording method, there is a concern that contact or collision with the probe will damage or abrade the ferroelectric recording layer. Accordingly, to prevent this, the providing of a protective layer on the ferroelectric recording layer and the forming of a lubricant layer on the ferroelectric recording layer have been proposed (see Japanese Unexamined Patent Publication (KOKAI) Heisei No. 9-198729 or English language family member U.S. Pat. No. 6,026,457 and Japanese Patent No. 4,141,745 or English language family member US2004/0027935A1, which are expressly incorporated herein by reference in their entirety).
The forming of a protective layer or lubricant layer on the ferroelectric recording layer as described above is an effective means of increasing the durability of the ferroelectric recording medium. However, the results of investigation by the present inventor have revealed that stable recording and reproduction sometimes become difficult with a recording medium in which a protective layer or the like has been formed on a ferroelectric layer in this manner.